Not applicable.
The semiconductor fabrication industry requires materials and deposition technology adequate to deposit metals, metal mixtures and metal compound mixtures in thin layers, plugs, vias and patterns on semiconductor and insulating or dielectric substrates to make appropriate electrical devices for integrated circuits, memory devices and flat panel display devices.
Various techniques are known for depositing metals, metal compounds and their mixtures on appropriate electronic materials substrates, including; physical methods (sputtering, molecular beam epitaxy, evaporation and laser ablation), alloying, and chemical vapor deposition (plasma, photo, radical or laser enhanced, low pressure and high temperature).
Various multiple metal oxides are known in the literature, including those recited in: xe2x80x9cAdvances in Processing of Ferroelectric Thin Filmsxe2x80x9d, L. M. Sheppard, Ceramic Bulletin, Vol. 71, No. 1, (1992), pp. 85-95; xe2x80x9cFormation of Al2O3xe2x80x94Ta2O5 Double-Oxide Thin Films by Low-Pressure MOCVD and Evaluation of Their Corrosion Resistances in Acid and Alkali Solutionsxe2x80x9d, Hara, et. al., Journal of the Electrochemical Society, 146 (2) (1999), pp. 510-516; xe2x80x9cHigh Coercivity in Sm2Fe17Nx Magnetsxe2x80x9d, Schnitzke, et. al., Appl. Phys. Left. 57 (26) Dec. 24, 1990, pp. 2853-2855; xe2x80x9cInvestigation of Ternary Transition-Metal Nitride Systems by Reactive Cosputteringxe2x80x9d, Van Dover, et. al., Chem. Mater. (1993), Vol. 5, pp. 32-35; xe2x80x9cReactively Sputtered Tixe2x80x94Sixe2x80x94N Films II. Diffusion Barriers for Al and Cu Metallizations on Sixe2x80x9d, Sun, et. al., J. Appl. Phys., 81 (2) Jan. 15, 1997, pp. 664-671; xe2x80x9cMOCVD Routes to Thin Metal Oxide Films for Superconducting Electronicsxe2x80x9d, Schulz, et. al., Adv. Mater. (1994), 6 No. 10, pp. 719-730; xe2x80x9cCompositional and Microstructural Characterization of RuO2xe2x80x94TiO2 Catalysts Synthesized by the Sol-Gel Methodsxe2x80x9d, Guglielmi, et. al., J. Electrochem. Soc., Vol. 139, No. Jun. 6, 1992, pp. 1665-1661; xe2x80x9cEnhancement of the Dielectric Constant of Ta2O5 Through Substitution with TiO2xe2x80x9d, Cava, et. al., Nature, Vol. 377, Sep. 21, 1995, pp. 215-217; and U.S. Pat. No. 4,058,430, the latter of which also discloses the deposition process known as xe2x80x9catomic layer epitaxyxe2x80x9d.
Chemical vapor deposition (CVD) has gained favor in recent years due to its properties of providing uniform and conformal deposition and its ability to deposit an array of materials under highly controllable conditions. Typically, chemical vapor deposition can provide high deposition rates of high purity materials in a controlled fashion.
However, chemical vapor deposition has several drawbacks which make its implementation challenging. Not all desired chemicals are sufficiently volatile to make themselves amenable to chemical vapor deposition. Some chemicals are solids at storage or delivery conditions. Some chemicals are too volatile for adequate storage and delivery.
The situation for chemical vapor deposition is further complicated by the need to co-deposit several chemicals such as in multiple metal chemical vapor deposition, such as multiple metal oxide chemical vapor deposition. It is possible for metal precursors to react with one another or for at least one metal precursor for CVD to be too volatile or too involatile, i.e., a solid.
To overcome these disadvantages of CVD, the prior art has used solvents to dissolve solid metal precursors or blend liquid, particularly viscous liquid, metal precursors for CVD.
U.S. Pat. No. 5,204,314 discloses a foraminous device for flash vaporization of liquid mixtures or solvent mixtures of metal precursors for CVD.
U.S. Pat. No. 5,820,664 describes various solvent mixtures of mixed metal compound precursors, which are useful for CVD.
However, solvent systems for liquid delivery for CVD are problematic because compatible, volatile solvents must be chosen. Solvents decrease the amount of effective reagent that is delivered for a given flow and time period. More importantly, solvents introduce yet another reagent into the sensitive reaction zone where delicate semiconductor and electronic device fabrication is being performed. The adverse effects of such solvent presence must be considered. Finally, solvents represent an environmental and cost factor. The solvent or its degradation products must be recycled, captured or treated subsequent to utilization.
International Patent Application WO98/46617 describes metal precursors and processes for deposition of metals from mixed xcex2-diketonates. The application addresses liquid delivery of metal precursors for CVD and other depositions by direct liquid injection. Using mixed xcex2-diketonates enhances the liquid state of the precursors to facilitate delivery. Solvents are an option for the liquid mixtures.
Similar disclosures appeared in xe2x80x9cNew Liquid Precursors for Chemical Vapor Depositionxe2x80x9d, Gordon, et. al., Mater. Res. Soc. Symp. Proc., 495, (1998), pp. 63-68; and xe2x80x9cLiquid Compounds for CVD of Alkaline Earth Metalsxe2x80x9d, Gordon, et. al., MRS Meeting, Apr. 7, 1999, San Francisco, Calif.
The prior art attempts to provide appropriate liquid media for metal precursor delivery have required the use of selected solvents or mixed xcex2-diketonate ligands to assure liquid conditions for delivery. Solvents constitute problems of contamination and abatement. Mixed ligands constitute problems of inadvertent ligand exchange which can lead to non-liquid conditions. The xcex2-diketonate ligands frequently lead to solid metal compounds absent manipulation of the xcex2-diketonate substituents to avoid conditions leading to solid conditions, thus aggravating the consequences of inadvertant ligand exchange. The present invention overcomes these drawbacks by using a solventless, common ligand mixture of metals in a liquid state for deposition preferably by direct liquid injection to avoid solvent and ligand exchange drawbacks for consistent deposition performance.
The present invention is a process for deposition of a multiple metal or metal compound layer on a substrate of an electronic material, comprising:
a) providing a solventless mixture of two or more metal-ligand complex precursors which constitute a liquid at ambient conditions, wherein the ligands are the same and are selected from the group consisting of alkyls, alkoxides, halides, hydrides, amides, imides, azides, nitrates, cyclopentadienyls, carbonyls, pyrazoles, and their fluorine, oxygen and nitrogen substituted analogs;
b) delivering the solventless mixture to a deposition zone where the substrate is located;
c) contacting the substrate under deposition conditions with the solventless mixture, where the contacting under deposition conditions is selected from the group consisting of chemical vapor deposition, spray pyrolysis, sol-gel processing, spin coating, and atomic layer deposition, and
d) depositing a multiple metal or metal compound layer on the substrate from the solventless mixture.
The present invention is more preferably a process for deposition of a multiple metal or metal compound layer on a substrate of an electronic material, comprising:
a) providing a solventless mixture of two or more metal-ligand complex precursors which constitute a liquid at ambient conditions, wherein the ligands of the precursors are the same and are selected from the group consisting of alkyls, alkoxides, halides, hydrides, amides, imides, azides, nitrates, cyclopentadienyls, carbonyls, pyrazoles, and their fluorine, oxygen and nitrogen substituted analogs;
b) delivering the solventless mixture by direct liquid injection to a flash vaporization zone to vaporize the solventless mixture;
c) contacting the substrate under deposition conditions with a resulting vapor of the solventless mixture, and
d) depositing a multiple metal or metal compound layer on the substrate from the solventless mixture.
Preferably, the ambient conditions are less than or equal to 40xc2x0 C. and less than or equal to 30 psig.
More preferably, the ambient conditions are 20-30xc2x0 C. and 5-6 psig.
Preferably, the solventless mixture is mixed with a source of oxygen prior to depositing the multiple metal compound layer on the substrate.
Preferably, the source of oxygen is selected from the group consisting of oxygen, ozone, nitrous oxide, nitric oxide, nitrogen dioxide, water, hydrogen peroxide, air and mixtures thereof.
Alternately, the solventless mixture is mixed with a source of nitrogen prior to depositing the multiple metal compound layer on the substrate. Alternately, the solventless mixture is mixed with a source of nitrogen and oxygen to deposit mixed-metal oxynitides prior to depositing the multiple metal compound layer on the substrate.
Preferably, the source of nitrogen is selected from the group consisting of nitrogen, ammonia, hydrazine, alkylhydrazine, hydrogen azide, alkylamine and mixtures thereof.
Preferably, the deposition process for producing a multiple metal or metal compound layer on the substrate from the solventless mixture is selected from the group consisting of chemical vapor deposition, spray pyrolysis, sol-gel processing, spin coating, and atomic layer deposition.
Preferably, the multiple metal or metal compound layer is selected from the group consisting of mixed metal alloys, mixed metal oxides, mixed metal nitrides, mixed metal oxynitrides, mixed metal carbides, mixed metal carbonitrides, mixed metal oxycarbonitrides, mixed metal oxycarbides, mixed metal borides, mixed metal sulfides, mixed metal phosphides, mixed metal arsenides, mixed metal antimonides, mixed metal selenides, mixed metal tellurides and mixtures thereof.
The present invention is also a composition for deposition of a mixed metal or metal compound layer, comprising a solventless mixture of at least two metal-ligand complex precursors, wherein the mixture is liquid at ambient conditions and the ligands of the precursors are the same and are selected from the group consisting of alkyls, alkoxides, halides, hydrides, amides, imides, azides, nitrates, cyclopentadienyls, carbonyls, pyrazoles, and their fluorine, oxygen and nitrogen substituted analogs.
Preferably, the mixture contains a first metal-ligand complex precursor which is liquid at ambient conditions and a second metal-ligand complex precursor which is liquid at ambient conditions.
Alternately, the mixture contains a first metal-ligand complex precursor which is liquid at ambient conditions and a second metal-ligand complex precursor which is solid at ambient conditions, but which is miscible in the first metal-ligand complex precursor.
Preferably, the metals of the solventless mixture of at least two metal-ligand complex precursors are individually selected from the group consisting of zinc, cadmium, mercury, aluminum, germanium, gallium, indium, thallium, tin, lead, antimony, bismuth, lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, silicon and cerium.
Preferably, the ligand of the solventless mixture of at least two metal-ligand complex precursors is selected from the group consisting of dimethyl amido, diethyl amido, ethylmethyl amido, butyl amido, dipropyl amido, methylpropyl amido, ethylpropyl amido, methoxy, ethoxy, propoxy, and butoxy.
Preferably, the solventless mixture of at least two metal-ligand complex precursors comprises Zr(N(CH2CH3)2)4, Sn(N(CH2CH3)2)4 and Ti(N(CH2CH3)24.
Alternately, the solventless mixture of at least two metal-ligand complex precursors comprises Zr(N(CH3)2)4, Sn(N(CH3)2)4 and Ti(N(CH3)2)4.
Further alternately, the solventless mixture of at least two metal-ligand complex precursors comprises Zr(O(C4H9))4, Sn(O(C4H9))4 and Ti(O(C4H9))4.
Further alternatively, the solventless mixture of at least two metal-ligand complex precursors comprises Ta(N(CH3)2)5 and Ti(N(CH3)2)4.
Further alternatively, the solventless mixture of at least two metal-ligand complex precursors comprises CH3CH2N=Ta(N(CH2CH3)2)3 and Ti(N(CH2CH3)2)4.
Further alternatively, the solventless mixture of at least two metal-ligand complex precursors comprises Al(OCH2CH3)3 and Ta(OCH2CH3)5.
Preferably, the solventless mixture of at least two metal-ligand complex precursors comprises Si(N(CH2CH3)2) and a metal-ligand complex precursor selected from the group consisting of Ti(N(CH2CH3)2)4, Zr(N(CH2CH3)2)4, Hf(N(CH2CH3)2)4, V(N(CH2CH3)2)5, V(N(CH2CH3)2)4, Nb(N(CH2CH3)2)5, Nb(N(CH2CH3)2)4, CH3CH2N=Nb(N(CH2CH3)2)3, CH3CH2N=V(N(CH2CH3)2)3, (CH3CH2N=)2W(N(CH2CH3)2)2, (CH3CH2N=)2Mo(N(CH2CH3)2)2, and CH3CH2N=Ta(N(CH2CH3)2)3.
Not Applicable
Multicomponent metal containing materials, such as mixed-metal oxides and nitrides often have unique physical properties that each individual metal oxide/nitride component does not possess. For example, some mixed metal oxides can be used for high dielectric constant materials, ferroelectrics, high temperature superconductors, catalysts, and corrosion resistant coatings. Also, some mixed metal nitrides show good diffusion barrier properties, superconducting, and magnetic properties.
In the electronics industry, as the size of integrated circuit (IC) devices becomes aggressively smaller, thin films deposited by chemical vapor deposition (CVD) demonstrate an advantage over physical vapor deposition (PVD) methods in terms of conformal coverage on various non-planar surfaces. In general, liquid precursors are preferred for CVD applications due to the ease and reproducibility in precursor delivery. Common precursor delivery methods used in CVD processing include vapor draw, bubbling with carrier gas, mist droplet (aerosol or spray) delivery, and direct liquid injection (DLI). DLI is particularly a preferred method for the delivery of multi-components because it delivers the same ratio of constituents to the reactor as are in the source container. DLI has the added advantage of storing the precursor at room temperature and heating only the amount required to be delivered, and therefore, improving precursor shelf life.
In the present invention, new liquid precursor mixture compositions are disclosed that can be used for precursor dispersing delivery methods, including DLI in CVD applications. The volatile components are chosen such that:
1) They are chemically compatible, therefore, no non-volatile polymeric or multinuclear species are formed;
2) No precipitates are generated due to ligand exchange on the metals or inter ligand reactions, i.e., the same ligand is used for all precursors (i.e., homoleptic, for the present invention, (RN)=M shall be deemed to be the same as M(NR2);
3) The mixtures maintain low viscosity and thermal stability; and
4) Undesired redox chemistry will not take place (eg. M+1+Mxe2x80x2+3xe2x86x92M+2+Mxe2x80x2+2).
Liquid mixtures can be prepared either by directly mixing liquid metal-ligand complexes or dissolving solid metal-ligand complex(es) in liquid metal-ligand complex(es). In these systems, no solvent is needed or desired to dissolve or dilute the precursor mixtures to achieve a total liquid phase of the resulting mixtures. A broad range of CVD precursor solutions using organic solvents have previously been used as precursors for thin film depositions. The present invention""s new solventless precursor mixtures lower the burden of abatement of the CVD effluent in the exhaust, because there is no extra volatile organic medium to be collected after the CVD processing. In addition, since no solvent is used in the liquid mixtures described herein, high throughput of metal containing vapor can be delivered into the CVD reactor. Thus, the overall CVD process using these new liquid precursor mixtures is more environmentally benign and cost effective than liquid injection delivery of precursor solutions stated in the prior art. In addition to CVD or MOCVD (metal-organic CVD), the liquid mixtures of the present invention are amenable to atomic layer deposition, spin coating, spray pyrolysis and sol-gel processes. In atomic layer deposition, an approximately single layer of precursor molecules are adsorbed on a surface. A second reactant is dosed onto the first precursor layer followed by a reaction between the second reactant and the first reactant already on the surface. This alternating procedure is repeated to provide the desired thickness of element or compound in a near atomic thickness layer. The substrate temperature can be controlled to avoid undesired deposition. In spin coating, a liquid media is dispensed onto a spinning substrate and allowed to dry by the action of heat or reaction, etc. In spray pyrolysis, mist droplets (aerosol) are formed followed by thermal or photolytical decomposition of the precursor. In sol-gel processes, hydrolysis and condensation of precursors is performed where the precursors are deposited on the target substrate by spinning, dipping or spraying. In CVD using DLI, the solventless mixture is delivered from storage at ambient conditions in a liquid state to a flash vaporization zone, where the solventless mixture is quickly heated to the metal-ligand complex precursors"" vaporization temperature, typically 100xc2x0 C. to 500xc2x0 C.
Deposition conditions will vary depending on the precursors to be reacted, the metals to be deposited and the substrate which is the target of the deposition. The appropriate deposition conditions of elevated temperature are preferably in the range of approximately 150-600xc2x0 C. More preferably, the appropriate deposition conditions of elevated temperature are approximately 200-500xc2x0 C. The deposition conditions also are preferably conducted at a deposition zone pressure in the range of approximately 0.01-50 Torr., more preferably, approximately 0.1-5 Torr. These constitute the respective deposition conditions for the various deposition processes occurring in a deposition zone, such as a reaction chamber.
The multi-component precursors are selected from the group consisting of, but not limited to, metal alkyls, metal alkoxides, metal halides, metal hydrides, metal amides, metal imides, metal azides, metal nitrates, metal cyclopentadienyls, metal carbonyls, metal pyrazoles, and their fluorine, oxygen and nitrogen substituted analogs. Preferably, the ligand of the solventless mixture of at least two metal-ligand complex precursors is selected from the group consisting of dimethyl amido, diethyl amido, ethylmethyl amido, butyl amido, dipropyl amido, methylpropyl amido, ethylpropyl amido, methoxy, ethoxy, propoxy, and butoxy. It is important to use the same or common ligands, homoleptic ligands, to avoid potential ligand exchange problems of the prior art. Preferably, the homoleptic ligands are monodentate.
The metal of the metal ligand precursor can be one or more of: zinc, cadmium, mercury, aluminum, germanium, gallium, indium, thallium, tin, lead, antimony, bismuth, lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, silicon and cerium.
The ambient conditions at which the solventless mixture of two or more metal ligand precursors must be liquid are defined as generally less than or equal to 200xc2x0 C., preferably less than or equal to 40xc2x0 C. and less than 30 psig. Preferably, the ambient conditions for liquid phase delivery are 20-30xc2x0 C. and 5-6 psig.
The solventless liquid mixture is introduced into the deposition zone and vaporized preferably at a temperature in the range of approximately 50-200xc2x0 C. More preferably, temperature is approximately 80-120xc2x0 C.
Appropriate choice of precursors, in the presence of oxidant or nitrogen containing reactant, would provide either mixed metal oxides, nitrides, and oxynitrides. In addition, using proper precursor mixtures and CVD conditions, it is also possible to grow mixed metal alloys, carbides, carbonitrides, oxycarbides, oxycarbonitrides, borides, sulfides, phosphides, arsenides, antimonides, selenides, tellurides, and mixtures thereof. The oxidant or nitrogen containing reactant includes but is not limited to: oxygen, ozone, water, hydrogen peroxide, nitrous oxide, nitric oxide, nitrogen dioxide, air, nitrogen gas, ammonia, hydrazine, alkylhydrazine, alkylamines and mixtures thereof.
In addition to thermal CVD, the above precursors could be used for plasma, laser radical, or photo enhanced CVD deposition, a well recognized deposition technique, or by atomic layer deposition. Furthermore, appropriate choice of liquid mixture precursors may also be applied to sol-gel processing, spray pyrolysis and spin coating of films.
Exemplary solventless mixtures of at least two metal-ligand complex precursors comprises Zr(N(CH2CH3)2)4, Sn(N(CH2CH3)2)4 and Ti(N(CH2CH3)2)4; or Zr(N(C3)2)4, Sn(N(CH3)2)4 and Ti(N(CH3)2)4; or Zr(O(C4H9))4, Sn(O(C4H9))4 and Ti(O(C4H9))4; or Ta(N(CH3)2)5 and Ti(N(CH3)2)4; or CH3CH2N=Ta(N(CH2CH3)2)3 and Ti)N(CH2CH3)2)4; or Al(OCH2CH3)3 and Ta(OCH2CH3)5; or Si(N(CH2CH3)2) and a metal-ligand complex precursor selected from the group consisting of Ti(N(CH2CH3)2)4, Zr(N(CH2CH3)2)4, Hf(N(CH2CH3)2)4, V(N(CH2CH3)2)5, V(N(CH2CH3)2)4, Nb(N(CH2CH3)2)5, Nb(N(CH2CH3)2)4, CH3CH2N=Nb(N(CH2CH3)2)3, CH3CH2N=V(N(CH2CH3)2)3, (CH3CH2N=)2W(N(CH2CH3)2)2, (CH3CH2N=)2Mo(N(CH2CH3)2)2, and CH3CH2N=Ta(N(CH2CH3)2)3.